For example, in a gear support shaft of a transmission of a vehicle including an engine, various types of rolling bearings, such as a deep groove ball bearing and an angular contact ball bearing, are widely used.
A ball bearing of this type includes the following as main components: an inner race having a radially outer surface in which an inner raceway surface is formed; an outer race arranged on an outer side of the inner race, and having a radially inner surface in which an outer raceway surface is formed; a plurality of balls interposed between the inner raceway surface of the inner race and the outer raceway surface of the outer race so as to be rollable; and a retainer arranged between the inner race and the outer race, for retaining the balls equiangularly. Any one of the inner race and the outer race is mounted to a stationary part such as a housing, and another one of the inner race and the outer race is mounted to a rotary part such as a rotation shaft.
When the ball bearing is used under oil bath lubrication, the rotating retainer acts like a compressor of a pump, and a lubricating oil is excessively drawn into an inside of the bearing through spaces between the retainer and the inner race and between the retainer and the outer race. The lubricating oil that is thus drawn is stirred in the inside of the bearing by the balls and the retainer, and hence resistance of the lubricating oil to stirring increases torque (heat generation) of the bearing. In particular, high-speed rotation of a motor is input in an electric vehicle and a hybrid vehicle, and hence the rotary part such as a rotation shaft tends to rotate at high speed. As a result, an influence of the above-mentioned resistance to stirring cannot be ignored.
In this context, there have been proposed various bearings including means for restricting an inflow of the lubricating oil into the inside of the bearing (for example, see Patent Literatures 1 and 2).
The bearing apparatus disclosed in Patent Literature 1 has the following configuration. Specifically, the labyrinth forming member having a disk shape is arranged in a press-contact state on the small-diameter-side end surface of the inner race so as to face the flange portion which is formed on the small diameter end side of the retainer to extend radially inward. The labyrinth structure is formed between the labyrinth forming member and the flange portion formed on the small diameter end side of the retainer. This configuration prevents the lubricating oil from being excessively drawn into the inside of the bearing.
Further, the rolling bearing disclosed in Patent Literature 2 has the following structure. Specifically, the narrow guide gap is formed between the retainer and the inner race and between the retainer and the outer race, and the lubricant-inflow-side end surface of the retainer is formed into the inclined surface. Further, the radially inner surface of the retainer is formed into the inclined surface. In the rolling bearing, the narrow guide gap is formed between the retainer and the inner race and between the retainer and the outer race, and the lubricant-inflow-side end surface of the retainer is formed into the inclined surface, and thus the lubricating oil is prevented from being excessively drawn into the inside of the bearing. Further, the radially inner surface of the retainer is formed into the inclined surface, and thus the lubricating oil, which excessively flows into the inside of the bearing, is actively discharged to an outside of the bearing.